DE3006767A1 - CONTROL DEVICE FOR EXHAUST GAS RECIRCULATION AMOUNT IN AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

Description:

The present invention relates to a control device for a motor vehicle, and more particularly a control device which controls the flow rate of exhaust gas in accordance with the operating condition an internal combustion engine is fed back or recirculated.

Exhaust gas recirculation in an internal combustion engine is carried out to reduce the amount of nitrogen oxides, which are generated in the exhaust gas. Conventional apparatus for doing this uses approximations of functions of engine load, such as the pressure differential between locations upstream and downstream of a throttle valve, the negative pressure in a carburetor nozzle, etc., by the degree of opening to control a valve, which in turn controls the recirculation of the exhaust gas. In such a device the recirculation of exhaust gases can then be set when the temperature of the cooling water for the engine is relatively low, and the properties of recirculation during heating can be adjusted by regulating the flow rate of exhaust gas can be adjusted. However, it is difficult to get the exact ratio of the recirculated exhaust gas for certain operational requirements, if one because of the economic Problems recirculating the exhaust gas using only a small number of parameters and a small number controls by valve actuators. Furthermore, there is a tendency that the recirculation of exhaust gas is carried out in operating areas in which exhaust gas recirculation is not required. An increase in the number of actuators and different probes for precise control becomes the problem the manufacturing defects increase here, resulting in a

030037/0680

unsatisfactory control and high manufacturing costs leads. If the specific characteristics of the internal combustion engine are changed, then it is a great deal effort and time required to replace and adjust the actuators.

It is therefore an object of the present invention to provide an exhaust gas recirculation control device which the difference between the desired and the actual operating parameters in the characteristic Properties of the exhaust gas recirculation greatly reduced.

The present invention provides an exhaust gas recirculation system for an internal combustion engine with a valve for controlling a flow rate of exhaust gas, which is returned from an exhaust outlet to an intake air inlet of the engine, a control device with the following characteristics:

a) a first sensor for determining the flow rate of the intake air to the engine,

b) a second sensor for determining the speed of the engine,

c) a first computer device for determining the fuel injection time from the output of the first sensor,

d) a memory in which a two-dimensional diagram of the exhaust gas recirculation quantities for a grid of points is stored, which represent the values of the engine speed and fuel injection time, and

e) a second computer device, which is set up to access the diagram and data in Agreement with the calculated fuel injection time and the measured engine speed determine and continue the data for controlling the valve.

030037/0680

The use of a two-dimensional table is permitted es / that the required throughput of recycled Exhaust gas is accurately determined at any point within the operating range, the requirement being eliminated will increase the number of actuators and therefore have problems with incorrect values in the devices used are avoided. A change in the special properties of the engine makes accordingly only the renewal of the hard drive used is required.

In the particular embodiment, it has been designed to improve control over steep or rapidly changing sections of the exhaust gas recirculation characteristics the grid / on to which the data values are specified / unequal divisions on at least one of the axes: namely the fuel injection time (φ) or the number of engine revolutions per unit of time (N).

According to another aspect of the present invention is to reduce storage requirements for areas / that do not require exhaust gas recirculation / and thus to simplify the feedback control of the areas, which is swept over by the diagram, made as small as possible, and if the operating data values outside the boundaries of the diagram, then the data values at the outer boundaries of the diagram are used to to stop the recirculation of exhaust gas.

According to a further aspect of the present invention is to increase the accuracy of the control and to Simplify arithmetic operations a data value that is not directly included in the diagram, calculated by linear interpolation of the four surrounding grid points.

030037/0680

According to yet another aspect of the present invention are for effecting correct control of exhaust gas recirculation in vehicles of the same type / but different Operating characteristics two types of grid point tables are used, which refer to the exhaust gas recirculation characteristics a manual and an automatic transmission are set to the different Have operational areas.

According to a particular aspect of the present invention the fuel injection time is derived from the flow rate the intake air in an internal combustion engine. The speed of the motor is measured. A desired The recirculation rate of exhaust gas is controlled by a central computer or Processor unit calculated from the fuel injection time and the engine speed by using a Uses memory that contains a two-dimensional diagram, with each grid point in the diagram being dependent on the Axes of the fuel injection time and the engine speed is determined and each grid point the value of the Contains desired recirculation amount of exhaust gas.

The above and other objects, features, and advantages of the present invention will be apparent from the following Description can be seen in more detail, which is used in connection with the accompanying drawings. In the Drawings is; '

Fig. 1 is a schematic view of a preferred embodiment the control device according to the invention for the exhaust gas recirculation,

FIG. 2 is a block diagram of the device according to FIG. 1,

3A and 3B each show a diagram which has a division with equal and unequal intervals, which is entered in a memory according to FIG. 2,

4A and 4B each show an illustration of the interpolation of data between raster points, and

030037/0680

Fig. 5 shows the reading of a fixed memory through a central processing unit.

The detailed description of the preferred embodiment now follows.

The same reference number indicates corresponding parts or elements throughout the drawings.

Reference is now made to FIG. 1; the basic concept of the control device 10 according to the invention for exhaust gas recirculation is shown taking a portion of the exhaust gas from an internal combustion engine 12 through an exhaust pipe 14, a Recirculation duct 16 and an exhaust gas recirculation valve 18 (hereinafter referred to as EGR valve), which is provided in the channel 16, returned to an intake pipe 20 will. The valve 18 includes a diaphragm 180 which has a Housing 182 divided into two chambers 184 and 186. The chamber 184 includes a return spring 188 which has a Valve body 200, one end of which is attached to membrane 180 and enclosed in chamber 186, biased in a direction to close the channel 16.

The suction pipe 20 is provided with an air filter 22, an air flow measuring device 24, a throttle valve 26 and a fuel injector 28, which Supplies fuel to the engine.

An auxiliary air valve 30 includes a diaphragm 310 which a housing 312 divides into two chambers 314 and 316. The chamber 314 contains a return spring 318, which the Diaphragm 310 is moved downward and an appropriate reference pressure from an output actuator 32 is applied a tube 34 receives. Chamber 316 is located between locations upstream and downstream of the throttle valve 26 through pipes 36 and 38 in connection. Thus moves

030037 / 068Ö

a valve body. 320 according to the pressure difference between the points upstream and downstream of the throttle valve 26 up and down. An air regulation device 40 has a valve body 410, the a channel 42 opens which connects between locations upstream and downstream of the throttle valve 26, but only during the cold state or when the engine is idling.

The actuating device 32 comprises a membrane 330 which divides a housing 332 into two chambers 334 and 336. the Chamber 334 communicates via pipe 44 with intake passage 20 at a point downstream from throttle valve 26 as well through an outlet pipe 46 with the pipe 34 in communication. The chamber 336 is maintained under atmospheric pressure and is provided with a return spring 338 which exerts pressure on the diaphragm 330. The actuator 32 is provided with a first actuating portion 32A, which is arranged in a channel 48, the one Communication between a point upstream of the throttle valve 26 and the outlet pipe 46 of the chamber 334 established. The operating portion 32A is provided with a diaphragm 340a and a vertically movable valve body 342a, which is attached thereto in a housing 344a. The valve body 342a is electromagnetically operated to open the channel 48 to open and close according to an instruction from a microcomputer, as described in more detail below to apply a desired reference pressure to chamber 314 of valve 30.

A second operating portion 32B has a similar one Structure like the first operating section 32A; the second Actuating portion 32B is arranged in a channel 50 which communicates between the control chamber 184 of the exhaust gas recirculation valve 18 and the end of channel 48 on the side of section 32A. Chamber 334 the output actuator 32 stands through

030037/0680

- ΊΟ -

Outlet pipe 52 with channel 50 'between section 32B and the valve 18 in communication. The operating portion 33B is provided with a diaphragm 340b and a vertically movable one Valve body 342b is provided which is attached thereto in a housing 344b. The valve body 342b becomes solenoid operated to open and close channel 50 according to instructions from the microcomputer close and thereby control the pressure inside the chamber 184 of the valve 18. This moves the valve body 200 vertical in order to control the flow rate of exhaust gas flowing through the pipe 16 from the exhaust side to the Intake air side is returned.

The exhaust pipe 14 is provided with a catalytic converter 54 (for example a three-way converter), which serves to remove harmful components of the exhaust gas.

A different type of analog control signals obtained during engine operation, such as the output signals from a throttle valve switch 56, a water temperature sensor 58 which measures the temperature of the cooling water for the engine, and an O ₂ sensor 60 in the exhaust pipe 14, are used as a group is input from control inputs 62 in the microcomputer 64. This microcomputer processes the set of control inputs 62 for controlling the output actuator 32 to open and close the EGR valve 18. A crank angle sensor 66 measures the rotation of the crankshaft 68 to input a reference pulse and an angle pulse is sent to the microcomputer 64 for each unit angle of engine rotation generated or released. The output 70 of the air flow meter 24, which represents the flow rate of the intake air to the engine 12, and a switching signal 72, which represents whether the transmission (not shown) is in the position of automatic transmission (A / T) or in the position of manually switched

.0.30037 / 068 0 ·

■ ■■■ - -: '-. ^: 300S767

Power transmission (M / T) is located, the microcomputer 64 is fed.

Reference is now made to FIG. 2; the basic control operation of the microcomputer 64 is shown by a block diagram shown. The outlet 70 of the air flow meter 24, which shows the flow rate of the intake air to the engine is represented by an analog / digital converter 640 in a circuit 642 with a high degree of integration (LSI circuit) into a corresponding digital output 644, which is fed to a central processing unit (CPU) 646, which calculates the desired flow rate of fuel by the fuel injection time T of the fuel injection valve is shown in the specific embodiment, and from the flow rate of the intake air that is assigned to the group of control inputs 62, such as the water temperature input from probe 58 to provide the calculated results to injection valve 28. The reference output and the angle output of the crank angle sensor 66 are determined by a counter 650 in the LSI circuit 642 are counted and fed to the central processing unit 646 to determine the number of rotations N of the motor per unit of time to determine. The following operation is based on the two signals T and N, which is a read-only memory (ROM memory) 648 used.

The one shown in the diagram within the symbol for the read only memory 648 is an exhaust gas recirculation area (EGR area) from a maximum limit value N "" the number of

Max

Engine revolutions per unit of time and a maximum base fuel injection time T is determined. There is a difference in EGR area between operations with manual power transmission M / T and automatic power transmission A / T before; the hatched and from one The solid line in the two-dimensional diagram applies to vehicles that are equipped with a manual gearshift

030037/0680

shoots are provided, while the wider range is up to the dashed line applies to vehicles that are equipped with an automatic transmission. A diagram that shown to the right of read only memory 648 represents that the EGR flow rates for M / T and A / T and thus the usage factors derived therefrom at the same point in the diagram of the read-only memory 648 differ from each other. The central processor unit uses the signals T and N as well as a signal that the Operation indicates M / T or A / T to address read only memory 648 and the data required to determine to be taken from the exhaust gas recirculation quantity.

The central processor unit 646 for its part supplies the exhaust gas recirculation quantity as a control signal to an output register 650 to. This register operates the output actuator 32 to the EGR valve 18 to a desired extent, as shown in FIG. The analog control inputs 62 mentioned above become the LSI circuit 642 supplied and from there as corresponding digital signals 652 to the central processor unit 646 in order to be as desired Normalization factors or scale factors for the amount of exhaust gas recirculation to be used.

In the special exemplary embodiment, the N and Τ subdivisions in the two-dimensional diagram which is stored in the _{read-only memory 648 are uneven.} For comparison, a diagram with divisions at equal intervals is shown in FIG. 3A, the close-lying curve sections encircled by a dashed line indicating a steep change in the exhaust gas recirculation amount. Accordingly, slight errors in the values of N and T in the diagram produce a relatively large error in the flow rate of the exhaust gas recirculation, which increases the possibility of the generation of harmful components in the exhaust gas. A two-

030037/0 6.8 0

dimensional.es diagram rewritten on unequal pitches is shown in Figure 3B, and it does not contain any steep or dense sections, with one accurate measurement is made possible.

Furthermore, in the special embodiment, those values N and T which correspond to sections of the diagram are which do not require exhaust gas recirculation, not stored. If the achieved numerical values are outside of the diagram, then the numerical values are at the outer limit indicated by the solid or dashed line is read and used to interrupt the exhaust gas recirculation, whereby the table and thus also the memory is reduced.

When the operating condition of the engine, i.e. a reference point P, is obtained by values N and T actually obtained is not on a grid point, as shown in FIGS. 4A and 4B, then the values on the four Surrounding points a, b, c and d around the point P are chosen as the object of the calculation and a linear, proportional interpolation is performed on the four points to obtain a value at point P. At this Calculation are the errors introduced by using a linear interpolation method very small, but the time savings are huge.

Fig. 5 shows the process, wherein the central processor unit reads the appropriate values from the read-only memory 654, if the two-dimensional diagram is stored with grid points with uneven spacing. Used initially the central processing unit an address look-up table 652 to find the address for T and N, and then uses these addresses to access the main look-up table or diagram 654. If interpolation is required then the lookup process is repeated four times and then that is

030037/0680

linear interpolation of the activity carried out.

In short, the procedure adopted in the present invention is performed as follows. First the program checks whether the starter switch (not shown) is on or off. When the switch is on becomes, then the engine is not in a steady state but under cranking control, and therefore will the exhaust gas recirculation valve 18 is fully closed. If the Starter switch is turned off, then a calculation is made for the fuel injection time T and the number N of Motor revolutions per unit of time. Then the required point is determined in the look-up table, and after choosing the correct table based on whether it is manual or automatic Gear is used, the data values are read and a linear interpolation is carried out. the Values at the outer limit of the table are used as control values for the sections outside the outer limits of the table, i.e. for the area in which exhaust gas recirculation is unnecessary. Thus, the exhaust gas recirculation amounts and the opening degrees of the exhaust gas recirculation valve certainly.

The present invention has the following advantages: First, the exhaust gas recirculation properties are used controlled to an extraordinarily high accuracy, with only operating actuators instead a conventional mechanical control or regulating device are required. Thus are the control devices not so involved manufacturing defects -. exposed and are uniform in quality as well as excellent in durability. The result is the exhaust gas recirculation quantities that correspond to the respective operating requirements suffice, with the effectiveness of fuel consumption being improved to a great extent. The Er-

030037/0680

set the exhaust gas recirculation properties in accordance with the respective special characteristics of the types of motor vehicles, transmissions and regulations of Countries to which the vehicles are sent can only be exchanged for the 648 and the arithmetic operation section of the central processing unit 646 is required.

Of course, the present invention would be described in terms of a preferred embodiment thereof, and various changes in their details will be apparent to those skilled in the art. For example, the memory in which the look-up table or diagram is stored is described as permanent storage, but it is also possible to use any other suitable memory device which also has a memory direct access, etc.

030037/0680

Blank page

Claims (8)

PATENTANViAί-ΤΕ "A. GRÜNECKER H. KINKELDEY OR-ING. W. STOCKMAIR DR-IPJG. 'AeC (CALTCCMI K. SCHUMANN P. H. JAKOB G. BEZOLD OR nm NAT. · BfVQCM 8 MUNICH MAXIMILIANSTRASSE P 14 758 NISSAN MOTOR COMPANY, LIMITED ■ Feb. 22. 2, Takara-cho, Kanagawa-ku, Tokohama-snl, Kanagawa-ken, Japan , Control device for the amount of exhaust gas recirculation in an internal combustion engine Patent claims: 1 J Control device for an exhaust gas recirculation system for an internal combustion engine, with a valve for controlling the flow rate of exhaust gases, which is carried out from an exhaust gas outlet to the intake air inlet of the engine, characterized by the following features: a) a first sensor (24) for determining a flow rate of intake air to the engine (12), b) a second sensor (66) for determining the speed (N) of the engine, c) a first computer device for determining the fuel injection time (T) from the output of the first probe., d) a memory (648; 654) in which a two-dimensional Look-up table of exhaust gas recirculation quantities for a grid of points is fed which the Represent engine speed values and fuel injection time, and 030037/0680 TBLEFON (O8B) 9998Ο9 TELEX 0B-9B38O TELEQRAMMB MONAPAT TBLEKOPIEReR e) a second computing device (646) which is set up for this purpose is to refer to the look-up table and get data corresponding to the fuel injection time determine which is calculated from the speed of the particular motor and the data for controlling the Valve (18) to run. 2. Control device according to claim 1, characterized in that that the point grid has values with uneven distances along at least one of the axes (Fig. 3B). 3. Control device according to one of claims 1 or 2, characterized in that the grid comprises the entire area in which exhaust gas recirculation is carried out will. 4. Control device according to claim 3, characterized in that the look-up table has at least one Has data value as the exhaust gas recirculation amount for values of the speed (N) of the engine (12) and the fuel injection time (T) which are outside the grid should be used. 5. Control device according to one of claims 1 to 4, characterized in that a data value is within a square or Rectangle formed by four neighboring data in the table by interpolation from the four surrounding ones Data is calculated (Fig. 4A). 6th Control device according to one of Claims 1-5, characterized in that that the table changes in its range in accordance with whether a manual transmission or an automatic transmission is used. 030037/0680 7. Control device according to one of claims 1 to 6, characterized in that the first sensor (24) the type determined according to the output type belongs to a type with an analog output, and that the first computer device an analog-to-digital converter (640) for converting the output of the first sensor into a corresponding one to convert to digital output (644). 8. Control device according to one of claims 1 to 7, characterized in that the second sensor has a. Crank angle sensor (66) comprises to provide as an output reference and angle pulses which determine the angle of rotation of the Engine and a counter (642) to count reference and angle pulses from the crank angle sensor. 030037/0680